1. Field of the Invention
The present invention relates to refuse recycling, and more particularly to plants and machinery for the efficient separation and handling of mixed refuse.
2. Description of Related Art
In the past, landfills were the primary waste disposal means. But fewer waste disposal sites, and increasingly stringent environmental regulations concerning air quality, landfills, and groundwater contamination now favor incineration. Incineration reduces and minimizes wastes by oxidizing and decomposing the matter. It has been successfully applied to industrial, municipal, and hazardous wastes that include organic substances that can undergo and sustain thermal degradation.
Incineration technology has been developing to meet tougher environmental standards. Technological advances include increases in efficiency and improvements in emissions control. After incineration, wastes are converted to carbon monoxide, carbon dioxide, water, and ash. Depending on the composition of the initial waste, compounds can be produced that include halogens, metals, nitrogen, and sulfur. The release of such compounds and carbon dioxide are highly regulated. The destruction efficiency for these hazardous wastes must usually be 99.9999%. So incinerators are equipped with afterburners, scrubbers, filtration units, and membranes.
The choice of which incinerator type to employ depends on the wastes' combustibility, and its characterization as liquid, sludge, solid, or gas. The wastes' ignition temperature, flash point, and flammability limits determine the necessary operating temperature, oxygen concentration, and residence time for greatest waste minimization. Common incinerator types include the rotary kiln, fluidized bed, liquid injection, multiple hearth, catalytic combustion, waste-gas flare, and direct-flame.
Rotary kiln, fluidized bed, and liquid injection incinerators can all be operated in an oxygen-starved mode, e.g., pyrolysis. High caloric value wastes, those with a high heat content, are most appropriate for this kind of operation. Multiple hearth incinerators use vertically shaped hearths, and are good for incinerating sewage sludge. They are operated from 1400-1800° F. Catalytic combustion, waste-gas flare and direct flame incinerators are used for burning gases. Catalytic combustors use a catalyst, and are best for low organic concentration wastes. Waste-gas flares are used for non-hazardous waste with high organic content. Direct flame incinerators operate from 1000-1500° F., and are used when the waste gas has particles.